Winona County and a mining company squared off Thursday before the Minnesota Court of Appeals over sand.

Not just any sand, but a silica mineral variety with very hard and round grains, perfectly suited for the petroleum industry for hydraulic fracturing operations, also known as "fracking." It's considered some of the highest quality silica sand in the country, according to Minnesota Sands LLC, the company mining it.

But Minnesota Sands, which leases about 3,000 acres in the area, can't mine the sand because Winona County banned sand mining for industrial purposes in 2016. Supporters of the ban objected to risks of pollution and to trucking the sand over local roads around the country.

"Minnesota Sands has spent years acquiring mineral interests and building the infrastructure to undertaking reasonable mining activity in Winona County. Local governments like Winona County cannot seal the border and ban the export of goods produced within the county while allowing the use and distribution of those goods solely to the local area," said Minnesota Sands attorney Chris Dolan.

"It's a hoarding of the natural resources of the sand, partly for economic reasons, partly for political reasons, to keep the sand out of the national marketplace," said Dolan. "Powerful local interests object to the use of these minerals in that national marketplace," he added, noting the controversial nature of fracking and the opposition to it by some environmentalists across the country.

Dolan told judges that was unconstitutional.

The three-judge appeals panel took up the case after a Winona County court upheld the county ordinance that effectively banned mining for fracking sand, although Dolan said it allows the same sand to be extracted by the same methods for other uses.

"Facially, the ordinance is discriminatory," Dolan told the judges, as he argued the company's appeal is also based on the argument that the regulations so diminished the value of the mines that it amounted to an illegal "taking" of the property.

Attorney Jay Squires argued on behalf of Winona County and said the county allowed sand mining for road construction, animal bedding and other uses but was specifically addressing the very large scale mining required for industrial petroleum fracking sand.

"The intent of the county was to assure that those high level, intense activities involved in industrial sand mining would not occur in the county," Squires said.

Squires also said that the ban didn't mean the county was depriving Minnesota Sands of its property rights. "There is no taking," Squires said. He said the company hadn't met other regulatory requirements to mine fracking sand, and effectively had no right to mine in the first place.

Judges Matthew Johnson, Renee Worke and Lucinda Jesson heard more than 40 minutes of argument. They're expected to rule within the next 90 days.